1. Field of the Invention
The present invention relates generally to vehicle suspension and more specifically to a front suspension which enables a reduction in the height of the front of the vehicle.
2. Description of the Prior Art
FIGS. 6 to 9 show examples of suspensions currently used in racing machines (disclosed in Motor Fan issue 81 published in June of 1987). In these types of suspension it is preferred to set the lever ratio defined between stroke of the spring 2 and the stroke of the shock-absorbed 3, close to or greater than 1.0.
the most recently used of these types of suspensions are the pull rod and push rod types shown in FIGS. 8 and 9.
FIG. 10 shows a double wishbone type front suspension arrangement of the type disclosed in the automotive magazine ATZ 88 (1986) July/August issue No. 409 wherein the spring is arranged about the shock absorber 6 and the latter is connected at its lower end to an upper link 7. In this arrangement the lever ratio which is defined by L2/L1 is about 0.7.
However, with this type of front suspension, if it is used in normal automotive vehicles the upper end of the shock absorber is located at a relatively high position and as result it is very difficult to lower the level of the hood. The reason for this is that in actual practice, the maximum of the shock absorber is about 215 mm+2.times.(bound stroke)+(rebound stroke). In racing cars the bound/rebound stroke is set about 50/50 (mm) while in normal type vehicles it is set at about 100/100 (mm). Accordingly, if this arrangement is used in normal type vehicles, the shock absorber is subject to abnormal elongation and again the level of the hood cannot be lowered in the required manner.
With the pull rod type arrangement shown in FIG. 8 the shock absorber 3, pull rod 4 and the bell crank lever 5 are arranged so as to attenuate the generation of horizontally acting moments at each of the pivots involved. However, in the case of a front wheel or four wheel drive, the drive shaft (not shown) it is necessary to make room for the shaft and arrange the pull rod either forward or aft of the drive shaft. Under these circumstances the reaction of the shock absorber, which is transmitted through the pull rod to the upper link, subjects the latter to a bias which acts in the longitudinal direction of the vehicle and induces an undesired compliance steer effect.
On the other hand, with the suspension shown in FIG. 10 in order to unify the force transmission ratio and the lever ratio L2/L1, it is necessary to produce a damping force which is roughly (L2/L1).sup.2 times the piston speed. As the piston speed varies with that of the bell crank, the piston falls in the lower speed zone and the shock absorber is unable to provide the required damping effect. Further, if the diameter of the wheel is 620 mm then the hood becomes excessively high at a height which can be calculated to be about 750 mm.
Further, in JP-A-64-1612 the shock absorbers are arranged to project laterally out from the vehicle chassis and are connected by way of a triangular link member in a manner that vertical displacement of the road wheel is converted into lateral movement which compresses the shock absorber.
However, with this arrangement as the triangular link member is pivotally connected to a member which is rigid with the vehicle chassis, the lateral stroke which compresses the shock absorber is smaller than the corresponding vertical stroke. This results in the compression stroke of the shock abosrber being reduced to the degree that required damping degree cannot be achieved.